flavor

For me, the epitome of stovetop alchemy is making caramel from table sugar. You start with refined sucrose, pure crystalline sweetness, put it in a pan by itself, and turn on the heat. When the sugar rises above 320°F/160°C, the solid crystals begin to melt together into a colorless syrup. Then another 10 or 20 degrees above that, the syrup begins to turn brown, emits a rich, mouth-watering aroma, and adds tart and savory and bitter to its original sweetness.

That's the magic of cooking front and center: from one odorless, colorless, simply sweet molecule, heat creates hundreds of
different molecules, some aromatic and some tasty and some colored.

How does heat turn sugar into caramel? Heat is a kind of energy that makes atoms and molecules move faster. In room-temperature table sugar, the sucrose molecules are jittery but standing in place, held still by the forces of attraction to their neighbors. As the sugar heats up in the pan, its molecules get more and more jittery, to the point that their jitters overcome the attractive forces and they can jump from one set of neighbors to another. The solid crystals thus become a free-flowing liquid. Then, as the temperature of the sugar molecules continues to rise, the force of their jittering and jumping becomes stronger than the forces holding their own atoms together. The molecules break apart into fragments, and the fragments slam into each other hard enough to form new molecules.

That's what I've thought for many years, along with most cooks and confectioners and carbohydrate chemists: heat melts sugar, and then begins to break it apart and create the delicious mixture we call caramel.

And we've all been wrong.

It turns out that, strictly speaking, sugar doesn't actually melt. And it can caramelize while it's still solid. So proved chemist Shelly Schmidt and her colleagues at the University of Illinois in studies published last year.

It's dismaying to think that so many could be so wrong for so long about such a basic ingredient and process! But it's also a rare opportunity to rethink the possibilities of the basic. Here's a plateful of possibilities; scroll down for more.

Professor Schmidt's group made their discovery when they tried to nail down the precise melting point of sucrose. The figures reported in the technical literature vary widely, and it wasn't clear why.

The melting point of a substance is the temperature at which it turns from a solid into a liquid while maintaining its chemical identity. When solid ice turns into liquid water, for example, the molecules of H2O move fast enough to escape the attractive forces of their neighbors, but they're still H2O. And it doesn't matter how fast the substance heats up: the melting point is the same. Ice melts at 32°F/0°C. Always.

After careful analysis, Professor Schmidt found that whenever sugar gets hot enough to turn from a solid into a liquid, some of its molecules are also breaking apart. So sucrose doesn't have a true melting point. Instead it has a range of temperatures in which its molecules are energetic enough to shake loose from their neighbors, and a range in which the molecules jitter themselves apart and form new ones. And these two ranges overlap. Whenever sugar gets hot enough to liquefy, it's also breaking down and turning into caramel. But it starts to break down even before it starts to liquefy. And the more that sugar breaks down while it's still solid, the lower the temperature at which it will liquefy.

When we make caramel standing at the stove, we use high heat to liquefy and then brown the sugar in a few minutes, and the liquefying temperature can be upwards of 380°F/190°C. But Professor Schmidt's group found that when they ramped up the heat slowly, over the course of an hour, so that significant chemical breakdown takes place before the solid structure gives way, the sugar liquefied at 290°F/145°C.

I made the caramelized sugars in these photos by putting crystals and cubes in my gas oven at around 250°F/125°C, shielding them with foil above and below to avoid temperature extremes from the cycling heating element, and leaving them there overnight and longer. In the large sugar crystals, which I got in a Chinese market, it's clear that breakdown and caramelization is fastest in the center. That may be because the center is where impurities get concentrated as the crystals are made, and the impurities then kickstart the breakdown process.

Caramel makers have long known that, as is true in most kinds of cooking, the key to caramelization is the combination of cooking temperature and cooking time. But the the temperatures have typically been very high, the times measured in minutes. Now we know that you can caramelize low and very slow and get something different. Sugar breakdown even occurs at ambient storage temperatures, though it takes months for the discoloration and flavor change to become noticeable. For a manufacturer this is undesirable deterioration. But for a cook in search of interesting ingredients, it could be desirable aging.

In a follow-up to her initial scientific reports, Professor Schmidt wrote in Manufacturing Confectioner that

from a practical point of view, caramelization can be thought of as browning of sucrose by applying heat for a length of time. Thus it may be possible to better control the caramelization reaction by identifying the time-temperature conditions that optimize the production of desirable caramel flavors compounds, while minimizing undesirable ones. Confectionery manufacturers and sugar artisans, armed with this new scientific knowledge, may be able to push their craft in unforeseeable directions.

While browsing among the vegetable starts at a nursery in Santa Cruz last year, I came across a flat of sugar beets. I'd never tasted sugar beets before. They're a special variety of Beta vulgaris bred for sugar production, with none of the colorful pigments of vegetable beets that would further complicate the manufacture of pristine white crystals. So I bought some seedlings and planted them. They grew well through nearly a year of benign neglect. Last month I dug them up and tried them out.

The beets I grew were irregular in shape and size, the largest weighing in at about a kilogram, or over 2 pounds trimmed of leaves and small roots. Both raw and roasted they had a mild beet flavor and were very sweet indeed. I used my refractometer, a handy instrument that measures the concentration of dissolved materials in liquids, to get a rough idea of the sugar levels in their juice. Most of the sugar beets ran between 15% and 18% dissolved solids, while store-bought red and chioggia beets were closer to 5%.

I was especially curious to see what a home version of beet sugar would be like. Refined white table sugar is manufactured from beets and from sugarcane by extracting the juices from the raw materials, evaporating off their water, and separating the sucrose sugars from everything else, including a host of other plant chemicals and byproducts of the evaporation process. That separation process involves the use of mineral lime, carbon dioxide, charcoal made from various materials (sometimes animal bone), and centrifuges.

Not for the casual sugar-maker! Instead I figured on making an unrefined sugar, a beet version of the delicious palm and cane jaggeries that come from Asia, or the cane panela (piloncillo, papelón) of Latin America, or North American maple sugar.

But I had my doubts about whether unrefined beet sugar would be anything close to delicious. I'd read that unlike the molasses left over from cane sugar manufacture, beet molasses is fit only for livestock feed. I wondered whether that's because the beet residues are intrinsically unpleasant, or are somehow made so by the particular way beets are handled. Where sugar cane grows above ground and is processed shortly after harvest, beets are dug from the soil, have that distinct earthy odor, and may be stored for months in piles 20 feet high, where they remain alive and can deteriorate. Even fully refined beet sugar sometimes ends up with off flavors.

I ended up making small batches of beet sugar in three different ways. Each time I started by washing the beets, and then trimming and peeling them--two steps not in the industrial flowchart that I hoped would minimize off flavors.

The first time around I ran the beets through a juicer, and got about half the starting weight in juice. Rather than boiling it down over high heat, I gently evaporated it in a gas oven set at 250oF. (Gas ovens are well vented, so evaporation-slowing humidity doesn't build up.) The juice quickly turned an unappealing brown-gray and developed a strong beet odor, probably due to browning enzymes and perhaps also enzymes that generate earthy-smelling volatiles. After a few hours, I had a beety sweet syrup that cooled into a dull-colored paste. It was edible, but not especially nice.

Next I shredded the beets in a food processor, simmered the shreds in three times their weight in water to extract their juices, strained out the shreds, and evaporated the liquid down. This syrup and paste had a pleasantly mild beet aroma, but they were still an unfortunate grayish brown.

Finally I tried precooking the beets to kill the enzymes before I shredded them and extracted the juices. I sliced the beets, rinsed them to remove enzymes from the surfaces, then microwaved the slices in batches so that they reached the boiling point quickly, in a couple of minutes. The syrup developed only a faint beet aroma and a light gray color that soon disappeared into a cool-toned brown.

All of the beet syrups and pastes were mainly sweet, but with an edge of acidity and saltiness from the other plant materials that were extracted and concentrated along with the sugars. When I cooked them down to the point that they turned dark brown, all had the pronounced acidity and bitterness of cane molasses along with its characteristic aroma, which mostly masked any beetiness.

So it is indeed possible to make a good unrefined sugar from a vegetable that can be grown almost anywhere. True, it's not very efficient to do so: evaporating off water burns a lot of energy for the amount of sugar you end up with. (At least you can use the beets efficiently: the greens are essentially the same as chard, and you can squeeze or pan-dry the spent shreds to remove excess moisture, add salt and a little of their own sugar to restore some taste, and then toss with starch or beaten egg to make beet hash browns or latkes).

But it's an interesting process and product. Along the way I learned that in the beet-growing areas of Germany, Zuckerrübensirup is sold as a spread and to flavor pumpernickel bread dough and sauerbraten. Earthy sweetness has its uses.

In this month's Curious Cook column, I write about making iced tea and coffee by preparing them with cold water instead of hot. Aficionados differ on the relative merits of cold- and hot-brewed drinks. Cold brewing does extract a different balance of flavors compared to a standard hot brew. If you think of them as different drinks, then you can enjoy each for its particular qualities. I also describe recent studies of tea made with jamaica, the outer flower parts of a kind of hibiscus, and give recipes for jamaica and "mojito" teas from Maricel Presilla of Zafra and Cucharamama in Hoboken NJ.__________________

Mayer, F. et al. Sensory study of the character impact compounds of a coffee beverage. European Food Research & Technology 2000, 211:272-76.

WHENEVER I’m flying home and the plane passes over the south end of San Francisco Bay, my eyes can’t linger long enough over its startling patches of orange and red.

They’re sea salt ponds, cultivated to produce pure snow-white sodium chloride for industry and for the table. The colors in the ponds come from unusual microbes that thrive in the evaporating brine and produce pigments to cope with the intense sunlight.

A few months ago I finally encountered the colors of that briny life up close, in a jar of salt from the Murray River region in southeastern Australia. The remains of salt-loving bacteria and algae give the crystals a beautiful pink blush and a faint, pleasant aroma.

These days, salts come from all over the world, in many hues and crystal forms and textures. But this welcome blizzard is borne on a whirlwind of obfuscatory hype.

In my first column of 2011 I write about the blizzard of specialty salts that now come our way from all over the world, and describe two recent academic studies that examine whether different salts actually do have distinctive tastes.

In today's Curious Cook column I write about what happens to the flavors of cooking oils when they're heated, and about the value of paying attention to oil flavor. It turns out that delicious and pricey extra-virgin olive oils lose much of their aroma in the pan. And stale, rancid oils are less healthful than fresh oils. I also mention the dismaying finding of researchers at the University of California at Davis that many American consumers prefer the flavors of defective olive oils to the flavors of high-quality oils--probably because they seldom get the chance to taste good oils!

Due to an editing error, the print edition of the column misstates the identity of the taste panel that tested the set of olive oils before and after cooking. It was the research panel of the University of California Cooperative Extension program, not a taste panel at U.C. Davis or its Olive Center. The web edition of the column has been corrected.

In today's column I write about the un-acids, ingredients that are alkaline and give unusual flavors and textures to a small but significant set of foods that includes pretzels, tortillas and tamales, Oreo cookies, and ramen-style noodles. Baking soda, sodium bicarbonate, is a weak alkali and not good for much more than leavening baked goods. But a brief baking in the oven converts soda into soda ash, sodium carbonate, a much stronger alkali and a good substitute for lye, which is so strong that it's best handled with gloves and goggles.

In my July 28 column I write about water as an ingredient that can enhance the flavors of strong spirits, cocktails, high-alcohol wines, and coffee. Added water has little or no flavor of its own, but it boosts the aroma of alcoholic drinks by diluting the alcohol and loosening its hold on aroma molecules, and makes delicate coffee aromas more noticeable.

Audrey Saunders of Pegu Club in New York has created a number of "inverted drinks" in which a spirit plays the supporting role to a lower-alcohol wine-based ingredient, rather than the usual other way around. Try her Intro to Aperol and also her Madeira Martinez, which is now one of my favorite cocktails.

In today's column I write about the flavor of fresh coriander leaves, and how it is that they can be eaten with pleasure in much of the world but taste inedibly soapy to many people in the U.S.

In the column I don't mention the recent study from Reyes et al (last reference below), which reports that cilantro leaf extracts damage DNA, and therefore that cilantro could be a long-term health hazard. These are very preliminary findings and no reason for fans to give up cilantro, but it's a subject worth following as more information comes in.

In today's Curious Cook column in the New York Times, I write about a distillation method for concentrating aromas that keeps them especially fresh. Vacuum or cold distillation is being used to manufacture distinctive new gins, and chefs and bartenders are adapting a tabletop lab device called a rotary evaporator to create startling new dishes and drinks. This exploration is going on in Europe and Asia, but not openly in the U.S., where distillations involving alcohol are effectively illegal. David Arnold, leading rotovap jockey and director of culinary technology at the French Culinary Institute in New York City, describes the virtues of vacuum distillation and why he thinks it should be legal.